Another way of changing out the front sight blade can be borrowed from the old Smith revolvers. Mill the blade down to the ramp, just as you did, then mill a narrow slot lengthwise in the ramp. For a front sight, make a blade out of some flat stock, width to taste, mill the tang to fit the slot in the ramp tightly, then drill two small pin holes, and pin into place. Make the blade overly tall and file height to fit.
For a rear peep I've been thinking of machining out a rear tang, inletting it into the wood, then tig welding it to the rear of the receiver, bedding the tang in JB to reinforce the stock cut, then drill and tap for what ever tang sight tickles your fancy. Don't know if I'll have time this summer to do all this yet, but if not winter starts about October 1st around here, then I'll have time.
There should be nothing wrong with silver soldering on a base to drill and tap at the breech end of the barrel, then putting on an Ashley style ghost ring sight either. Should make a dandy style slap down rig for a slug gun.
Doubletap